Passive sensor



FIG. 1 is a perspective view of a passive sensor showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof, the left side view being symmetrical to the right side view;

FIG. 4 is a top plan view thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a passive sensor, as shown and described. 